Field of the Invention
The present invention relates to a liquid ejection head for ejecting a liquid such as an ink.
Description of the Related Art
In recent years, an ink jet (IJ) printer has been used in not only household printing, but also commercial printing for business or retail photo, or industrial printing for electronic circuit drawing or panel display, and its use has been spread. A head of the IJ printer used in the commercial printing or the industrial printing is strongly required to be capable of printing at a high speed. In order to realize this requirement, it is frequently employed to drive a recording element generating energy for ejecting a liquid ink at a higher frequency or to provide a line head having a width longer than the width of a recording medium and a great number of ejection orifices.
PCT Japanese National Publication No. 2010-521343 discloses the construction of a long line head in which a plurality of recording element substrates are arranged in zigzag. In the construction in which the plural recording element substrates are arranged in zigzag, a recording element substrate having a parallelogram plane shape may be used in some cases for making the size of the head in a conveying direction of a recording medium small. In the invention disclosed in PCT Japanese National Publication No. 2010-521343, an electric wiring board is arranged at only a position opposing to one side portion of the recording element substrate, thereby attempting more miniaturization of the head. Examples of the electric wiring board include FPC (Flexible printed circuit) and TAB (Tape automated bonding).
The recording element substrate and the electric wiring board are electrically connected to each other with a connecting member such as, for example, a bonding wire to send or receive electric power or an electric signal. The connecting member is generally sealed and protected with a thermally curable resin for the purpose of preventing damage caused by external force or erosion caused by a liquid. When the connecting member is present at only one side portion of the recording element substrate and sealed with the resin, a sealing member composed of the resin is present at only one side portion.
In the invention disclosed in U.S. Pat. No. 6,609,786, a recording element substrate is mounted on an individual support member to fabricate a head module (unit), and a plurality of the head modules are arranged in a row to fabricate a long line head. The plane shape of each head module disclosed in U.S. Pat. No. 6,609,786 is rectangular, and the respective modules are diagonally inclined and arranged in such a manner that adjoining head modules overlap with each other in both a direction and a direction intersecting perpendicularly to the longitudinal direction to arrange the head modules at a high density.
In the liquid ejection head of the construction disclosed in PCT Japanese National Publication No. 2010-521343, in which the sealing member composed of the thermally curable resin for sealing the connecting member is formed at only one side portion of the recording element substrate, positional deviation of the recording element substrate may occur in some cases. The sealing member composed of the thermally curable resin is cured by heating. However, it is thereafter shrunk by cooling. Stress is generated upon shrinkage of the sealing member, and the positional deviation of the recording element substrate is caused by influence of the stress pulling the recording element substrate toward the side of the sealing member. When the recording element substrate deviates from an appropriate position, the impact position of a liquid ejected deviates, and so good recording cannot be conducted. This problem is similarly caused in such a line head having plural recording element substrates as disclosed in PCT Japanese National Publication No. 2010-521343 and even in what is called a serial type head in which a liquid is ejected while a small-sized liquid ejection head having only one recording element substrate is being moved. In particular, in such a line head that plural recording element substrates are arranged in a row as disclosed in PCT Japanese National Publication No. 2010-521343, the above-described problem is caused on the individual recording element substrates, and lowering of ejection accuracy (impact accuracy) due to lowering of relative positional accuracy between the recording element substrates is also caused. When such a liquid ejection head is employed in an ink jet printer, stripes or irregularities are caused on an image formed by liquid ejection to deteriorate image quality. In particular, formation of a very high-definition image has been conducted by an ink jet printer in recent years, so that it is desirable to eliminate even slight positional deviation of a recording element substrate which has heretofore not been taken into account so much. In addition, in the construction disclosed in PCT Japanese National Publication No. 2010-521343, the plural recording element substrates are installed on one long support structure, and so the whole head becomes unusable even if one of the plural recording element substrates becomes defective.